Packaging laminates based on cardboard and paper

Abstract

A folded moisture and heat resistant container is manufactured of a material of laminate type in the form of a sheet or a web, said laminate comprising at least a base layer ( 1 ), an outer coating ( 2 ) and an inner coating ( 3 ). The material is at least on one side thereof heat treated in an autoclave. In the material the case layer ( 1 ) consists of a liquid absorbing material, the outer coating ( 2 ) consists of a polymer selected from the group including polypropylene, oriented polypropylene, metalized high density polyethylene, linear low density polyethylene, unmodified polyester, metalized polyester and amorphous polyester, and the inner coating ( 3 ) consists of a polymer selected from the group including polypropylene, high density polyethylene, linear low density polyethylene, unmodified amorphous polyester.

What is claimed is: 
     
       1. A method for packaging and stabilizing a food product consisting essentially of the steps of:
 providing an open container from a sheet or web comprising a laminate including a base layer formed from a liquid absorbing material selected from the group consisting of paper and cardboard, at least one outer layer comprising a first polymeric material and facing the outside of said container, at least one inner layer comprising a second polymeric material and facing the inside of said container and at least one barrier layer comprising aluminum between said base layer and said inner layer, said open container being formed by heat sealing the sheet or web to itself; 
 adding a food product to the inside of the open container under non-aseptic conditions; 
 closing the container opening and thereby sealing the inside of the container from exposure to external microbial attack; 
 exposing the outside of the container to moist heat at autoclaving temperature; 
 maintaining said exposure to said moist heat for a time sufficient to heat said container and said food product to a temperature providing stabilization of said food product via sterilization while simultaneously retaining a level of dimensional stability and mechanical strength in said container for transport and subsequent storage of said container; and 
 thereafter allowing the container and the food product contained therein to cool, 
 wherein said polymeric material in said inner and outer layers each has a melting point sufficiently high to withstand exposure to said moist heat in a manner consistent with said dimensional stability and mechanical strength of said sealed container, and 
 wherein said inner layer polymeric material and said outer layer polymeric material are selected from the group consisting of polypropylene and oriented polypropylene.